2001 LB7 Question crank no start Question

[Nixxk]

Decided to restore my dads old 2001 LB7 , its been sitting for a while.
For trying to start this truck, i am by-passing the fuel tank and i have a lift pump under the hood with a yellow fuel tank and have the return going in there also ( from the quick connection under the hood ). i got Torque App on a tablet and after i remove the air in the system via bleed screw ( new fuel filter and new filter "housing/Holder" thing) and start cranking i get the Actual Fuel Pressure above the Desired Fuel Pressure on the Torque app. So i should be OK from the fuel stand point.

My question is , Should we see the Pulse Width (ms) of the injector or the balance rate while cranking ?? Mine are all zero's while cranking

Where i stand is i think i have a electrial issue cause if i stick a multimeter in the Fuel heater or MAF positive in the truck connector (any pink wire really ) i get a get a short to ground(multimeter set to continuity test and i measure from pink wire to ground of vehicle) ..... no expert here but i don't think a +12 Supply should be shorted to ground... so i am working my way back on all the pink wires to see where i have it shorted... crazy that no fuse as blown

Long story short ( too late ) i am hoping that the "shorted" pink wire is not letting the FICM fire the injectors.... well that's what i am hoping at this point.

but anyways back to the question.. should i see injectors "trying" to fire (see the millisecond's go to anything but 0) on my torque app while cranking ?

thanks
Nick

 

[Ron Nielson]

I don't have 2001 wiring, but here is how you get the 2003 wiring. GM doesn't change tons of wiring from year to year, so this may be good enough to answer your question

https://www.gmupfitter.com/wp-content/uploads/2021/05/2006_LD_CKFullSizeElectrical.pdf

 

[Nixxk]

HI Ron , Awesome Thank you , I do have Mitchells Electrical drawing but look like there is a ton more information in that PDF you linked

 

[2004LB7]

Just remember, GM changed a lot going into 2003 with the electrical on these vehicles. So there will be lots of diagrams in that PDF that don't apply. Unless you are really familiar with them the knowing which ones are the same or similar will be difficult.

We can't really help you with the wiring unless you tell us what wires you are trying to diagnose. Pink isn't going to do much good without the module or sensor to go with it

I've always seen zero on the balance rates during cranking. But you should see desired mm3 main rate. Can and crank sensors are a common electrical related item that can prevent the engine from starting. They don't always throw codes either

 

[Nixxk]

Just remember, GM changed a lot going into 2003 with the electrical on these vehicles. So there will be lots of diagrams in that PDF that don't apply. Unless you are really familiar with them the knowing which ones are the same or similar will be difficult.

We can't really help you with the wiring unless you tell us what wires you are trying to diagnose. Pink isn't going to do much good without the module or sensor to go with it

I've always seen zero on the balance rates during cranking. But you should see desired mm3 main rate. Can and crank sensors are a common electrical related item that can prevent the engine from starting. They don't always throw codes either

Thank you Jason Very much , that pointed me in the right direction.
Lots of learning on my side.
I still did not have it going but hopefully narrowing it down..

Yeah i know i was not clear on my wiring issue but i was mostly looking for the what actually shows up on the scanner while cranking
but here is what i learned... the Pink wiring that goes all over the engine and sensor goes to ground when the key is off position ... so i don't have a short to ground all over the pink wiring system... live and learn.

- Running a fuel tank on the top of the engine with a lift pump connected to the quick connect on the rear of engine driver side. with the return going the same tank and do the bleed thing a few times to make sure the air is all out and primer is hard.
- RPM at crank is 200 RPM
- Desired fuel pressure is 43 mpa , Actual fuel pressure goes to 50 mpa ish and more


Haven't been home so could not keep looking at things.
Next Step :
- Cam sensor
- Test the mm3 fuel rate.

 

[Nixxk]

HI Folks
Here is some updates.
Well i decided to get a more modern scanner tool ... launch cpr123x , was hopping to see the fancy fuel pressure graph while cranking ...
I ran a diagnostic on it .. and gave me 2 codes that the torque app and a old school obd2 code reader did not give.

the one of interest was P1631 : anti theft issue so fuel is not enabled. (something like that ). well turns out because i had the batteries out for so long it trigged to Anti theft to forget you key or key barrel ... so i did the "relearn for this vintage of truck
- try to start ... leave key to ON
- keep key on for 10 mins ,
- key off for 10 sec
- Repeat 3 times

She started right up after the 3rd cycle of this procedure.
it takes over 30 mins to do this so make sure you have a good battery or have the charger connected.

 

[2004LB7]

Thanks for the update. Security light should have tipped you off when it didn't go away after a few seconds with the key on

 

[Nixxk]

Thats the thing.. it did go away .. Even when i did the re-learn procedure the documentation mention that you should see the security light during the 10 min process and mind was off.
Anyways really happy she's going.. now going the rabbit hole of CFR and balance rate
Thanks
Nick